1. Field of the Invention
The present invention relates generally to a microstructure for sensing or applying a force and more particularly to a microsensor or a micromechanical actuating device comprising a thin film of lead zirconate titanate (PZT) as the active sensing or actuating material. The present invention also relates to a method of making such a microsensor or micromechanical actuator.
2. Description of the Prior Art
Microsensors such as accelerometers, pressure sensors, infrared detectors and chemical reaction sensors have been made using piezoelectric thin films such as zinc oxide and integrated circuit processing technologies. Micromechanical actuating devices have also been made using similar thin films together with integrated circuit processing techniques commonly known in the art as micromachining. These prior microsensors and micromechanical devices have been based on the piezoelectric properties of the zinc oxide thin film. The piezoelectric properties of a material relate to the interaction of mechanical and electrical stress-strain variables in such material. For example, compression of a material having piezoelectric properties generates an electrostatic voltage across the material, and conversely, application of an electric field across the material will cause the material to expand or contract in certain directions.
The above described microsensor devices function by detecting and measuring electrostatic forces developed in the zinc oxide film as a result of certain stresses or forces acting on the film. Because the electrostatic forces are proportional to the stresses on the film, the magnitude of the stress or force can be determined. The micromechanical devices provide selected mechanical movement or force resulting from the provision of an electrostatic force across the film. By controlling the electrostatic force, a mechanical movement or force of a certain magnitude can be developed. Although these prior art piezoelectric devices are acceptable for certain applications, they suffer from severe problems of low force and high friction. Thus, their applications are quite limited. Accordingly, there is a need in the art for microsensors and micromechanical devices based on piezoelectric properties which overcome the severe limitations of current materials and films.